In 1995, practice guidelines recommended a limit of 48 hours after the onset of atrial fibrillation (AF) for cardioversion without anticoagulation.1- 3 Whether the risk of thromboembolic complications is increased when cardioversion without anticoagulation is performed in less than 48 hours is unknown.

METHODS

In the retrospective Finnish CardioVersion study,4 all patients with a primary diagnosis of AF, aged 18 years or older, with successful cardioversion in the emergency department within the first 48 hours of AF, and residence in the catchment areas of Turku and Kuopio university hospitals from 2003 to 2010 and Pori central hospital during 2010 were included. Clinical details and the occurrence of thromboembolic complications within 30 days after cardioversion were retrospectively collected from medical reports.

The primary outcome, a thromboembolic event, was defined as a clinical stroke or systemic embolism confirmed by computerized tomography or magnetic resonance imaging, surgery, or autopsy. Time to cardioversion was determined as the difference between the beginning of arrhythmic symptoms to the exact time of cardioversion. If the duration of arrhythmia was uncertain, the cardioversion was excluded. Procedures were divided into groups according to the time to cardioversion: less than 12 hours (group 1), 12 hours to less than 24 hours (group 2), and 24 hours to less than 48 hours (group 3).

The protocol was approved by the ethics committees of the Hospital District of Southwest Finland and the National Institute for Health and Welfare, with a waiver of informed consent. Bivariable comparisons between groups were performed with the χ2 test, the Fisher exact test, or the Wilcoxon nonparametric test. Multivariable logistic regression analysis with a repeated-measures model was conducted to evaluate risk factors for thromboembolic complications, including comparisons between groups 2 and 1 and between groups 3 and 1.

Clinical features (age, female sex, heart failure, and diabetes) with independent predictive value for thromboembolic complications were used as covariates in the multivariate analysis based on our previous work.4 Statistical analyses were performed using SAS version 9.3 (SAS Institute Inc). Two-sided differences at P < .05 were considered significant.

RESULTS

Of 2481 patients with acute AF, 5116 successful cardioversions were performed without anticoagulation. The mean age was 61.0 (SD, 12.4) years, 1638 were female (32.0%), and 2434 had more than 1 risk factor for stroke (47.6%). Thirty-eight thromboembolic events occurred in 38 patients (0.7%; 95% CI, 0.5%-1.0%); 31 were strokes. The incidence of thromboembolic complications increased from 0.3% in group 1 to 1.1% in group 3 (P = .004, Table 1).

The incidence of thromboembolic complications according to the time to cardioversion in subgroups is presented in Table 1. In multivariable logistic regression analysis (Table 2), time to cardioversion longer than 12 hours was an independent predictor for thromboembolic complications (odds ratio of 4.0 [95% CI, 1.7-9.1] between groups 2 and 1 [P = .001]; odds ratio of 3.3 [95% CI, 1.3-8.9] between groups 3 and 1 [P = .02]).

DISCUSSION

Stroke is the most serious complication of AF. After the recommended 3 weeks of therapeutic anticoagulation, the stroke risk in elective cardioversion of AF ranges from 0.3% to 0.8%.1 In our study, the risk of thromboembolic complications was 0.7% when cardioversion was performed without anticoagulation within 48 hours of AF onset.

However, we found that a delay to cardioversion of 12 hours or longer from symptom onset was associated with a greater risk of thromboembolic complications (1.1%). When the duration of AF was less than 12 hours, the risk of thromboembolism was low (0.3%) without anticoagulation. The main limitation of this retrospective study lies on the verification of AF duration based on real-life evaluation in the emergency department.

Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This research was supported by the Finnish Foundation for Cardiovascular Research (Helsinki, Finland), and the Clinical Research Fund of Turku University Hospital (Turku, Finland).

Role of the Sponsor: The Finnish Foundation for Cardiovascular Research and the Clinical Research Fund of Turku University Hospital had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: The findings and conclusions of this report are those of the authors and do not necessarily represent the official position of the the Finnish Foundation for Cardiovascular Research or the Clinical Research Fund of Turku University Hospital.

REFERENCES

Fuster
V, Rydén
LE, Cannom
DS,
et al; American College of Cardiology/American Heart Association Task Force on Practice Guidelines; European Society of Cardiology Committee for Practice Guidelines; European Heart Rhythm Association; Heart Rhythm Society. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(7):e257-e354.PubMed | Link to Article

References

Fuster
V, Rydén
LE, Cannom
DS,
et al; American College of Cardiology/American Heart Association Task Force on Practice Guidelines; European Society of Cardiology Committee for Practice Guidelines; European Heart Rhythm Association; Heart Rhythm Society. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(7):e257-e354.PubMed | Link to Article

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